randombytes: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/randombytes - from package: cjdns

You may install the required package with command yum install {package}
Error in other languages:
randombytes: bevel nie gevind nie
randombytes: comandă negăsită
randombytes: comando não encontrado
randombytes: commande introuvable
randombytes: command not found
randombytes: käsku ei ole
randombytes: không tìm thấy lệnh
randombytes: komanda nerasta
randombytes: Kommando nicht gefunden.
randombytes: kommandot finns inte
randombytes: komut yok
randombytes: nie znaleziono polecenia
randombytes: níor aimsíodh an t-ordú
randombytes: no se encontró la orden
randombytes: no s'ha trobat l'ordre
randombytes: opdracht niet gevonden
randombytes: parancs nem található
randombytes: perintah tidak ditemukan
randombytes: príkaz nenájdený
randombytes: příkaz nenalezen
randombytes: команда не найдена
randombytes: командата не е открита
randombytes: 命令找不到
randombytes: コマンドが見つかりません